Chain door lock



FIG. 1 is a perspective view of a chain door lock showing my new design in an unlatched condition;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a front elevational view thereof; and,

FIG. 7 is a perspective view of the chain door lock of FIGS. 1-6 shown in a latched condition, the broken-line showing a fragment of a door and frame being for illustrative purposes only and forming no part of the claimed design. 

The ornamental design for a chain door lock, as shown and described. 